A fieldwork consisting of two faces, forming a salient angle, and two parallel flanks. See Bastion.
- Architecture A small, circular or crescent-shaped opening in a vaulted roof.
- Architecture A crescent-shaped or semicircular space, usually over a door or window, that may contain another window, a sculpture, or a mural.
- A fortification that has two projecting faces and two parallel flanks.
- A broad, low-lying, typically crescent-shaped mound of sandy or loamy matter that is formed by the wind, especially along the windward side of a lake basin.